1. Field of the Invention
The present invention relates to a boring apparatus for laminated plates and more, particularly, to a boring apparatus that is especially suitable for boring multi-layer plates.
2. Description of the Prior Art
A multi-layered substrate has been recently employed to form an electronic circuit within a limited area and volume.
To produce a multi-layered substrate, a prepreg (i.e., an insulating material in which two surfaces with spun glass fibers woven thereon are coated with uncured epoxy resin) is sandwiched between substrates and then subjected to pressing and heating. To accurately position the prepreg with respect to the substrates, it is necessary to bore holes in the prepreg, in advance, with the holes being adapted for receiving reference pins. Prepregs are normally bored in a multi-layer, packaged form to prevent contamination which leads to defective energization. In addition, copper foils are coated on upper and lower surfaces of the multi-layered substrate, and these copper foils also need be bored in advance.
Thin plates which need to be bored in advance, other than the prepreg and copper foils described above, are increasingly being used in a number of technical fields. Therefore, a need has arisen for development of means capable of accurately boring holes in such materials.
One heretofore known means for boring thin plates such as prepregs, copper foils and the like, is press means. Press means involves placing plates, one by one, on a press, and then punching the plates with a die. This poses a problem in that the efficiency of boring work is low, resulting in contamination of both sides of the plate. Another problem, especially for the aforesaid prepreg, is that a package needs to be unpacked to prevent contamination.
Another conventional boring means is drilling means. The use of drilling means involves placing plates in a laminated fashion on a drilling machine and cutting and boring them by means of a drill having a spiral groove or the like. This has an advantage in that the efficiency of boring work is good and less contamination in plates occurs, at least as compared with the aforementioned press means. However, a separate problem is created, in terms of work accuracy, in that the plates become fused together due to frictional heat between the drill and the plate, and chips thereby become fused around bored holes. Particularly, since the copper foil is pliable in nature, there is a problem in that distortion or burrs occur around a bored hole. A further problem is that since chips of the like are scattered due to the rotation of a drill or the like, maintenance of the drilling apparatus, especially cleaning, is time-consuming. Chips not cleaned away can adhere to parts of the drilling apparatus and lessen the durability thereof.